Safety needle assembly

ABSTRACT

The invention relates to a safety needle assembly for injecting a fluid into a human body comprising a cylindrical housing with a bottom surface supporting a needle cannula and a shield telescopically movable relative to the housing. A spring located within the housing urges the shield in a distal needle covering direction and a locking member also provided inside the housing moves simultaneously with the shield during injection and automatically locks the shield in a position where the sharp end of the needle cannula is concealed thereby irreversible immobilizing the safety needle assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/307,045filed on Nov. 29, 2002 and claims the benefit of priority of USprovisional application 60/343,045, filed Dec. 22, 2001 and DanishApplication PA 2001 01772, filed Nov. 30, 2001, under 35 U.S.C. 119 andU.S. application Ser. No. 10/307,045 filed on Nov. 29, 2002 under 35U.S.C. 120; the contents of all of which are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

The invention relates to a safety needle assembly, which reduces therisk of accidental needle-stick injuries, and especially a safety needleassembly where a needle cannula is mounted in a hub.

DESCRIPTION OF RELATED ART:

Needle assemblies are commonly used to either inject substances into orextract substances out of human or animal bodies. Such needle assembliesare typically disposable and are discarded after only one use. Theproblem presented by the disposal of a needle assembly, and indeed, byany handling of the needle assembly, is the potential risk of beinginjured by the sharp end of the needle cannula. This is particulardangerous when following after the penetration of a patients skin sincethe needle cannula then may be contaminated and therefore capable ofspreading diseases such as hepatitis and HIV.

A great number of safety needle assemblies has been developed where theneedle cannula is concealed by a telescopically movable shield duringthe injection.

One such prior art needle protection system is disclosed in WO 01.76665.This safety needle comprises a hub with a centrally located needlecannula. A telescopically movable shield is provided on the outsidesurface of the hub. The shield is telescopically movable between a firstposition where it fully covers the needle cannula and a second positionwhere a part or the needle cannula is left free to perform an injection.A cam element, rotatable mounted to the hub is provided with at leastone cam, which cam is guided in cam curve provided in the inside surfaceof the shield. The shield is urged in the distal direction by a springcocked between the hub and the shield. The cam curve is adapted to blockthe cam in a blocking position when the shield returns to the firstposition after an injection has been performed.

The safety needle assembly disclosed in WO 01.76665 is however rathercumbersome and consist of a large number of parts that must be mouldedand afterwards fitted together very precisely in order to obtain thecorrect movement of the cam follower.

It is also a fact that the different plastic parts of an assembledconstruction have a tendency to change the relative dimensions when theconstruction is sterilized using steam or gas. This is especiallycritical when the tolerances have to be very narrow, as in the safetyneedle assembly disclosed in WO 01.76665.

In order to assure that the cam element of WO 01.76665 in fact shiftsinto the locked position when the protective cap moves back to theinitiate position after an injection has been made, a rather powerfulspring is needed. This is an inconvenience for the user, since the userhas to press the protective cap in the proximal direction literally withthe use of his or hers skin while making the injection.

DESCRIPTION OF THE INVENTION:

It is henceforth an object of the present invention to provide a safetyneedle assembly, which overcomes the inconveniences of the prior artsafety needle assemblies, and especial to provide a safety needleassembly which is made from fewer parts, and which parts are not subjectto very strict tolerances.

It is further an objective of the present invention to provide a safetyneedle assembly having a spring with only a limited force therebyoffering the user maximum comfort.

In order to overcome the drawbacks of the prior art it is suggested toprovide the safety needle assembly with a separate locking elementlocated between the spring and the shield according to claim 1.

When the locking element is provided as a separate element locatedbetween the spring and the shield and moved simultaneously with theshield, the locking protrusion can be guided during the longitudinalmovement of the locking member thereby eliminating the need for tracksor cams thus making it possible to construct the safety needle assemblyfrom only three plastic part in addition to the hub.

Since there are no tracks or cams as such the internal tolerances arenot that important, and the friction can be kept rather low whichrenders it possible to utilize a somewhat soft spring, which enhancesthe user comfort.

By blocking the rotational movement of the locking protrusion with a finprovided on the inside surface of the housing as specified in claim 2,it is possible to define when the rotatable movement of the lockingprotrusion should commence simply by specifying a specific length of thefin.

Once the locking protrusion on the locking element has passed over theend of the fin as specified in claim 3 it will be impossible to move thelocking protrusion backwards. The length of the fins can be made suchthat once the shield has been activated and the needle cannula hasemerged from the opening in the shield it will be impossible to abortthe injection and keep the needle for later use.

When the locking protrusion engages the toothed ring of the shield asdefined in claim 4, the shield can be moved all the way back in theproximal direction thereby uncovering the needle cannula.

When the injection is over and the locking protrusion is arrested in theopening in the longitudinal rib as mentioned in claim 5, it is virtuallyimpossible to advance the needle cannula again by pressing the shieldbackwards in the proximal direction.

The guiding means for guiding the locking protrusion comprises onlyhorizontally defined ribs and fins as specified in claim 6. This makesboth the moulding of the parts and the assembly of the parts verysimple.

By mounting the shield inside the housing as disclosed in claim 7, it isensured that the shield cannot be separated from the housing.

When the spring cocked between the locking element and the hubinterfaces both the locking element and the bottom surface of thehousing as revealed in claim 8, it is ensured that the spring can beadded to the assembly in a very simple manner.

By providing the housing with a window through which the lockingprotrusion can be viewed when it is in the arrested position, it isensured that a user can visible inspect whether the safety needleassembly has been used before or not.

The part of the shield and/or the locking element that are visiblethrough the window when the safety needle assembly is in the unusedcondition can also be coloured in a colour indicating that the safetyneedle assembly is ready for use.

The window can either be transparent or simply an opening in thesidewall of the housing.

In the present context, the term “moving simultaneous” which are used todescribe the relationship between the movement of the shield and thelocking element, does not necessary mean that the shield and the lockingprotrusion moves with the same speed. The relative speed of movement isdefined by the various angled surfaces, and is therefore variable. Theterm “moving simultaneously” merely means that both the shield and thelocking protrusion move at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained more fully below in connection with apreferred embodiment and with reference to the drawings in which:

FIG. 1 Shows a perspective view of the safety needle assembly accordingto the invention.

FIG. 2 Shows an exploded view of the safety needle assembly according tothe invention.

FIG. 3 Shows a perspective view of the needle shield.

FIG. 4 Shows a perspective view of the locking element.

FIG. 5 Shows a perspective view of the body of the housing.

FIG. 6 Shows a schematically view of the body of the housing.

FIG. 7 Shows a schematically view of the safety needle assemblyaccording to the invention.

FIG. 8 Shows a schematically view of the safety needle assemblyaccording to the invention, with a part of the housing cut away.

FIG. 9 Shows the locking protrusion in its first position.

FIG. 10 Shows the locking protrusion in or moving towards its secondposition.

FIG. 11 Shows the movement of the locking protrusion moving from thesecond to the third position.

FIG. 12 Shows the locking protrusion in the third position.

FIG. 13 Shows a perspective view of an embodiment of the safety needleassembly according to the invention.

FIG. 14 Shows a part of the housing of an embodiment of the safetyneedle assembly according to the invention.

FIG. 15 Shows an exploded view of the safety needle assembly accordingto the invention.

FIG. 16 Shows a perspective view of the safety needle assembly stored ina container.

The figures are schematic and simplified for clarity, and they just showdetails, which are essential to the understanding of the invention,while other details are left out. Throughout, the same referencenumerals are used for identical or corresponding parts.

DETAILED DESCRIPTION OF EMBODIMENT

Initially it may be convenient to define that, the term “distal end” ismeant to refer to the end of the safety needle assembly inserted intothe patient, whereas the term “proximal end” is meant to refer to theend connected to the injection device.

FIG. 1 shows a safety needle assembly comprising a housing 1 and ashield 2, the housing 1 is made up from a hub 3 and a body 4. The hub 3and the body 4 is normally glued or welded together.

The connecting surface 5 between the hub 3 and the body 4 is in thefigures shown in a specific position, but could off cause be located aswanted. The hub 3 and the body 4 could even be moulded as one piececlosed at the top surface 6 by a lit. The top surface 6 is provided withan opening 8 through which the shield 2 appears.

The shield 2 is provided with a needle outlet 7 through which the needlecannula 30 can penetrate. The proximal end of the shield 2 is, as shownin FIG. 2, provided with eight outwardly projecting studs 10, whichstuds 10 has a planar fore front 11 and an angled back front 12.

The housing 1 has a bottom surface 9 in the centre of which the needlecannula 30 is mounted. The needle cannula 30 can either be mounted suchthat a part of needle cannula 30 projects from the bottom surface 9 inthe proximal direction, which is preferred for use with cartridges, orit can be mounted without this so called back needle, which is preferredfor hypodermic syringes. Adjacent the bottom surface 9, at the proximalend of the housing 1, means are provided for mounting the safety needleassembly on to an injection device. These means would normally be athread 35 such that the safety needle assembly can be screwed onto a pensyringe.

FIG. 3 shows the shield 2 seen from the proximal end. The eight studs 10are separated from each other by eight equally sized spaces 26. Theangular back front 12 of the studs 10 forms together with the shield 2 atoothed ring 13 where the centre of the studs 10 forms the tops and theshield 10 within the spaces 26 forms the valleys.

The locking element 16 seen in FIG. 2 is on the proximal outside surfaceprovided with four locking protrusions 17. These locking protrusions 17have, as shown in FIG. 4, an angled fore front 18 and a planar backfront 19.

The body 4 of the housing 1 is in FIG. 5 shown in perspective and inFIG. 6 in a sectional view. The body 4 is provided with four windows 20and one longitudinal rib 21 for each window 20. The ribs 21 are providedon the inside surface of the body 4. These longitudinal ribs 21 extendthrough the entire length of the body 4 although divided into two parts(21 a, 21 b) by the windows 20. The distal part of this rib 21 ismoulded uniform with a collar 24 provided at the distal end of the body4 and terminates in a planar surface 14 at the distal end of the window20. The proximal part of the rib 21 terminates at the proximal end ofthe window in a blocking surface 15, the use of which will be explainedlater. At the distal end of the body 4 there is provided four fins 22.These fins 22 is moulded uniform with the collar 24 at the distal end ofthe body 4, and has at the proximal end an angled surface 23 whichterminates approximately in a position adjacent the middle of thewindows 20.

Although the embodiment here described has eight studs 10, four lockingprotrusions 17 and four windows 20, these parts could be provided in adifferent number, as shown in FIG. 15.

When the safety needle assembly shown in FIG. 2 is assembled, a spring25 is cocked between the bottom surface 9 of the housing 1 and thelocking element 16 urging the locking element 16 and the shield 2 in adistal direction. The planar forefront 11 on the studs 10 abuts thecollar 24 such that the shield 2 is connected to the body 4 of thehousing 1.

The assembled safety needle assembly is shown in FIG. 7 and 8. FIG. 8illustrates the inside of the safety needle assembly with the body 4 cutaway.

The shield 2 is located such within the body 4 of the housing 1 thateach rib 21 and each fin 22 is located in the space 26 between two studs10. The upper part 21 a of the ribs 21 are however not shown in FIG. 8,since this upper rib 21 a is not entirely necessary. The locking element16 is thereafter mounted such that the angular forefront 18 on eachlocking protrusion 17 abuts the angled back front 12 on four of thestuds 10 of the shield 2, whereby the side surface of the lockingprotrusion 17 and the side surface of the studs 10 forms a straight linewhich line abuts the side surface of the fins 22 of the body 4 of thehousing 1.

Once the shield 2 and the locking element 16 is correctly mounted withinthe body 4 of the housing 1, the spring 25 is located around the needlecannula 30 and the body 4 and the hub 3 are sealed together, renderingthe safety needle assembly ready for use.

The movement of the locking protrusion 17 is schematically shown in FIG.9-12, showing the relative position of one of the locking protrusion 17on the locking element 16, two of the studs 10 on the shield 2, one ofthe fins 22 on the inside surface of the body 4 of the housing 1 and oneof the ribs 21 also located on the inside surface of the body 4 of thehousing 1.

FIG. 9 illustrates the safety needle assembly in its initial position,as shown in FIG. 8, with the shield 2 in its distal position where theshield 2 covers the needle cannula 30. When the shield 2 is pressedtowards the skin of a user, the shield 2 and with it the studs 10, aremoved in a proximal direction as indicated with the arrow 27. Thismovement also moves the locking protrusion 17 on the locking element 16in the proximal direction against the force F of the spring 25.

Once the locking protrusions 17 is moved free of the fins 22, as shownin FIG. 10, the angled fore front 18 of the locking protrusions 17 willslide along the angled back front 12 of the studs 10 and the angled forefront 23 of the fins 22 as indicated with the arrow 28. This movementwill move the locking protrusions 17 into contact with the valleys ofthe toothed ring 13. Further movement of the shield 2 and thereby thestuds 10 in the direction of the arrow 27 will only move the lockingprotrusions 17 further in the proximal direction. The injection is thenexecuted with the shield 2 in its most proximal direction. The positionof the fins 22 and the ribs 21 is such that the studs 10 are alwaysguided either by the fins 22 or by the ribs 21.

When the injection is over, the needle cannula 30 is retracted from theskin of the user, which will cause the shield 2 with the studs 10 andthe locking element 16 with the locking protrusion 17 to move in thedistal direction due to the impact of the force F executed by the spring25. The arrow 29 in FIG. 11 indicates this movement.

FIG. 12 illustrates how the force F of the spring 25 urges the lockingelement 16 with the locking protrusion 17 and the shield 2 with thestuds 10 in the distal direction. When the angled fore front 23 on thefins 22 aligns the angled back front 12 of the studs 10, such that thetwo angled fore fronts 23, 12 form a diagonal line, the angled forefront 18 of the locking protrusion 17 will slide along this line into aposition where the locking protrusion 17 is located between the upperpart 21 a and the lower part 21 b of the ribs 21 i.e. between the planarsurface 14 of the upper part 21 a of the ribs 21 and the blockingsurface 15 of the lower part 21 b of the ribs 21. In this position thelocking protrusion 17 and hence the locking element 16 and the shield 2is irreversible locked.

At the proximal end of the locking protrusion 17, the planar back front19 will abut or at least be blocked by the blocking surface 15 on theribs 21 of the body 4 of the housing 1, thereby rendering it impossibleto move the shield 2 in the proximal direction. At the distal end, theangled fore front 18 of the locking protrusion 17 will abut the toothedring 13 of the shield 2 and since the planar forefront 11 of the studs10 on the shield 2 abuts the collar 24 of the body 4 of the housing 1 itwill not be possible to move the shield 2 in the distal direction.Sideways the studs 10 of the shield 2 will be arrested between the upperpart 21 a of the ribs 21 and the fins 22. As a result of this it will beimpossible to move the shield 2 in any direction.

Instead of having the angled fore front 18 of the locking protrusion 17in abutment with the toothed ring 13 of the shield when the injection isover, the front end 36 of the locking element 16 can be design to abutthe inner top end 37 of shield 2 once the locking protrusion 17 is inthe locking position. This will make it virtually impossible to squeezethe angled fore front 18 of the locking protrusion 17 by pushing theshield 2 in the proximal direction.

The body 4 of the housing 1 is provided with four windows 20 whichwindows 20 divides each of the four ribs 21 into an upper part 21 a anda lower part 21 b. When the safety needle assembly has been used, thelocking protrusion 17 on the locking element 16 will be located betweenthe upper part 21 a and the lower part 21 b of the ribs 21, and willthus be visible through the window 20. The locking protrusion 17, or apart of it, could be coloured in an inflammatory colour, or providedwith another indication, which will render it very easy for a user tovisibly inspect whether the safety needle assembly has been used or notjust by glancing at the windows 20. The windows 20 could e.g. beprovided as openings in the wall of the body 4.

Prior to use, the safety needle assembly is delivered to the usersterilized and contained as is shown in FIG. 7. The container 31 isclosed at the distal surface 32 and open at the proximal surface 33. Theproximal surface 33 is sealed by a not shown removable seal. Thecontainer 31 has on the inside surface not shown ribs that mates ribs 34located on the outside surface of the housing 1 preferably on the hub 3,such that the safety needle assembly can be screwed on and off a pensyringe without removing the container 32 from the safety needleassembly. Further the container could on the inside surface be providedwith a number of not shown raised points supporting the safety needleassembly in a somewhat floating position making it easier for the steamor gas to fully surround the safety needle assembly during sterilizationin case this type of sterilization is used.

The spring 30 urging the locking element 16 and the shield 2 in thedistal direction is preferably made from stainless non-corrosive steelsuch that the spring 30 will not be damaged during the steamsterilization process. A spring 30 particular suitable for this purposeis a 1.4462/SAF2205 spring.

Another embodiment of the safety needle assembly according to theinvention is disclosed in FIG. 13 and FIG. 14.

FIG. 13 shows a housing 40 comprising of a hub 41 and body 42. Mountedinside the housing 40 are a shield 43 and a locking element 44. Theshield 43 penetrates out of the housing 40 through an opening 45 locatedat the distal end of the housing 40

The shield 43 is provided with four studs 46 and ends at the proximalend in a toothed ring 38.

This toothed ring 38 engages a second toothed ring 39 located on thelocking element 44. The locking element 44 is further provided with alocking protrusion 49 located at the proximal end thereof.

The needle cannula 30 is in FIG. 13 mounted in the bottom surface 50,which bottom surface 50 is provided in the housing 40, preferably in thehub 41.

FIG. 13 shows the safety needle assembly with the shield 43 in thelocked position, and FIG. 14 illustrates the inside surface of thehousing 40 by showing the part of the housing 40 cut away in FIG. 13seen from the backside.

The four studs 46 on the shield 43 is guided in first horizontal tracks51 provided on the inside surface of the housing 40. The lockingprotrusion 49 on the locking element 44 abuts a planar surface 48 in itsinitiate position and is guided in a second horizontal track 52 as theshield 43 is moved in the proximal direction. Once the shield 43 hasbeen moved all the way back to its most proximal position and theinjection is executed, a not shown spring positioned between the bottomsurface 50 and the locking element 44 will urge the locking element 44and hence the shield 43 in the distal direction. During this movement,the angled fore front 47 of the locking protrusion 49 will engage adiagonal track 53 also provided in the inside surface of the housing 40.While the shield 43 moves back to its initiate position, the lockingelement 44 and hence the locking protrusion 49 will rotate approximately180 degrees in the diagonal track 53 and engage a locking chamber 54provided at the distal end of the diagonal track 53, which lockingchamber 54 has a blocking surface 55 that a planar back front 56 of thelocking protrusion 49 will abut rendering further movement of the shield43 impossible. The first toothed ring 38 of the shield 43 and the secondtoothed ring 39 of the locking element 44 support this movement due tomutual engagement of the angled surfaces of the two rings 38, 39.

The shield 43 cannot be rotated relatively to the housing 40 due to theengagement of the studs 46 with the first horizontal tracks 51. Sincerotation of the shield 43 is inhibited it is impossible to rotate thelocking protrusion 49 of the locking element 44 backwards in thediagonal track 53, and the locking protrusion 49 will therefore remainin the locking chamber 54 thus rendering the safety needle assemblysecured.

A window could be provided in the housing 40 through which window thelocking chamber 54 can be viewed, such that the user can get a visibleindication whether the safety needle assembly has been used or not.

An improved embodiment of the safety needle assembly disclosed in FIG. 1to 12 is shown in FIG. 15 and in FIG. 16.

In the following the numbers referring to the same element as in theprevious figures has been given the same number plus one hundred.

The safety needle assembly shown in FIG. 15 comprises a housing made upfrom a needle hub 103 and a body 104 both preferably injection mouldedfrom PP. Both the hub 103 itself and the tower of the hub 103 issomewhat higher than shown in FIG. 2, while the body 104 is somewhatshorter. The needle cannula 130 is inserted in the tower of the hub 103and glued to the hub 103 by a blob of glue 160.

The body 104 is in this embodiment provided with three windows 120 andthe locking element 116 is also provided with three locking protrusions117. When the locking element 116 locks the safety needle assembly fromreuse, the three locking protrusions 117 will be visible in the threewindows 120 as earlier explained.

The shield 104 which is preferably made from TPX can be transparent suchthat the tip of needle cannula 130 is visible for inspection by the userprior to injection, has on its proximal end six studs 110. The toothedring 113 formed between these studs 110 is therefore in this embodimentonly provided with six valleys.

The locking element 116 which is preferably made from POM or PP is onthe distal end surface provided with a serrated ring 161 which are usedduring the manufacturing process. When the safety needle assembly isbeing assembled a tool can enter the safety needle assembly through theneedle outlet 107 in the shield 102 and engage this serrated ring 161 inorder to rotate the locking element 116 to the correct position beforethe shield 102 and the locking element 116 is permanently encapsulatedin the housing. For this purpose the needle outlet 107 needs to be largeenough for the toll to pass through the needle outlet 107.

In the embodiment shown in FIG. 10 there exist a slight possibility ofrotating the shield 2 when the studs 10 are longitudinal located betweenthe fins 22 and the lower part 21 b of the ribs 21. In order to preventsuch accidental rotation, the studs 110 of the embodiment shown in FIG.15 is provided with an additional guiding rib 162 which are guided in anumber of not shown guiding tracks provided on the inside surface of thebody 104 of the housing. Due to this no rotation between the shield 102and the body 104 is possible,

When the safety needle assembly is assembled the whole unit is packed ina container 131 which container 131 is sealed with a removable seal 163and sterilized. The removable seal 163 is preferably made from paper.

The distal part of the container 131 can be formed as a cup 164 holdinga predetermined volume as shown in FIG. 16. The dosage of an injectiondevice to be used with the safety needle assembly can thus be controlledby ejecting a predetermined number of doses into the cup 164 andverifying the expelled volume. This can be done either by filling theentire cup or by having indications printed on the cup 164.

Some preferred embodiments have been shown in the foregoing, but itshould be stressed that the invention is not limited to these, but maybe embodied in other ways within the subject matter defined in thefollowing claims.

List of parts:

-   1 Housing-   2 Shield-   3 Hub-   4 Body-   5 Connecting surface-   6 Top surface-   7 Needle outlet-   8 Opening-   9 Bottom surface-   10 Stud-   11 Planar ore front of studs-   12 Angled back front of studs-   13 Toothed ring-   14 Planar surface-   15 Blocking surface-   16 Locking element-   17 Locking protrusion-   18 Angled front of locking protrusion-   19 Planar back front of locking protrusion-   20 Window-   21 Rib-   21 a Upper part of rib-   21 b lower part of rib-   22 Fin-   23 Angled surface-   24 Collar-   25 Spring-   26 Spaces on shield-   27 Directional arrow-   28 Directional arrow-   29 Directional arrow-   30 Needle cannula-   31 Container-   32 distal surface of container-   33 proximal surface of container-   34 Ribs on outside surface of housing-   35 Thread-   36 Front end of locking protrusion-   37 Inner top end of shield-   38 Toothed ring of shield-   39 Second toothed ring of locking element-   40 Housing-   41 Hub-   42 Body-   43 Shield-   44 Locking element-   45 Opening-   46 Studs-   47 Angled fore front of locking protrusion-   48 Planar surface-   49 Locking protrusion-   50 Bottom surface-   51 First horizontal track-   52 Second horizontal track-   53 Diagonal track-   54 Locking chamber-   55 Blocking surface-   56 Planar back front-   102 Shield-   103 Hub-   104 Body-   107 Needle outlet-   110 Stud-   113 Toothed ring-   116 Locking element-   117 Locking protrusion-   120 Window-   125 Spring-   130 Needle cannula-   131 Container-   160 Glue-   161 Serrated ring-   162 Guiding rib-   163 Seal-   164 Cup

1. A Safety needle assembly comprising: a cylindrical housing having atop surface and a bottom surface, said housing having means for mountingsaid housing onto a medical injection device, a needle cannula mountedin the bottom surface, said needle cannula having a distal end locatedat a distal side of the bottom surface. a shield telescopically movablerelatively to the housing for movement between a distal position wherethe shield covers the distal end of the needle cannula and a proximalposition where at least a part of the distal end of the needle cannulais exposed, a spring located inside said housing urging the shield inthe distal direction, a locking element provided inside the housing andhaving at least one outwardly pointing locking protrusion wherein saidlocking element is a separate part provided between the spring and theshield and longitudinal moved simultaneously with the shield relativelyto the housing during use, whereby the locking protrusion provided onthe locking element is guided from a first position where the shield isin the distal position, via a second position where the shield is in theproximal position to a third position where the shield is in the distalposition and in which third position at least one of the lockingprotrusions is blocked by a blocking surface provided on the insidesurface of the housing whereby further movement of the shield isirreversible immobilized,
 2. A safety needle assembly according to claim1, wherein the locking protrusion of the locking element in the firstposition abuts a stud provided on the shield and a fin provided on theinside surface of the housing.
 3. A safety needle assembly according toclaim 2, wherein the locking element and the locking protrusion rotatesrelatively to the housing and the shield when an angled surface of thestud aligns an angled surface of the fin.
 4. A safety needle assemblyaccording to claim 3, wherein the locking protrusion of the lockingelement in the second position abuts a toothed ring provided at theproximal end of the shield.
 5. A safety needle assembly according toclaim 4, wherein the locking protrusion of the locking element in thethird position is arrested in an opening in a longitudinal rib providedon the inside surface of the housing, which opening defines the blockingsurface.
 6. A safety needle assembly according to claim 5, wherein theguiding means for guiding the locking protrusion of the locking elementcomprises the ribs and the fins provided on the inside surface of thehousing, which ribs and fins extends only in the horizontal direction.7. A safety needle assembly according to anyone of the claim 1 whereinthe shield is mounted inside the housing and penetrates through anopening at the top surface of the housing.
 8. A safety needle assemblyaccording to claim 7, wherein the spring interfaces the locking elementand the bottom surface of the housing.
 9. A safety needle assemblyaccording to claim 8, wherein the housing is provided with a windowthrough which window the locking protrusion is visible when the lockingprotrusion is in its third position.